The present invention relates generally to collapsible drums for building or fabricating multiple-ply tire carcasses, and more particularly to such drums for use in the fabrication of carcasses for the manufacture of high profile tires, especially of the multiple bead variety.
Collapsible tire building drums which have been found to be particularly suitable for the assembly of tire carcasses thereon are of the radially collapsible type. These collapsible drums are rotatable about a central axis and are usually formed of a plurality of elongated, axially extending arcuate drum segments which are coupled to a central hub arrangement by a pivotable linkage mechanism. The hub arrangement and the linkage mechanism coact with the drum segments to provide an essentially uninterrupted cylindrical surface for the assembly of the tire carcass and, thereafter, the collapse of the drum by the displacement of the drum segments towards the rotational axis so that the assembled tire carcass can be removed from the drum.
Tire carcasses assembled on collapsible drums and used for the manufacture of pneumatic tires normally include tire components such as multiple plies of tire bands, yarns, and one or more annular wire tire beads at opposite ends of the tire bands. Tire carcasses used for the manufacture of low profile tires e.g. highway type tires, usually have only a single wire bead at each end of the carcass and also provide a relatively small difference in bead diameter to carcass diameter on the tire building drum. Thus, the beads at opposite ends of the tire carcass, are of a diameter sufficiently close to that of the carcass on the drum so that the drum can be adequately collapsed to permit removal of the tire carcass from the collapsed drum. On the other hand, in the assembly of tire carcasses used for the manufacture of tires of the high profile type, such as off road, heavy truck, aircraft, and other multiple-bead tires, there is a relatively large difference in the ratio of the carcass diameter on the drum to the bead diameter. To fabricate such tire carcasses with previously known equipment, the collapsible drum was usually provided with radially inwardly extending tire bead rings to provide the relatively deep under cut bead flanges required for seating the wire beads, especially multiple-beads, at opposite ends of the tire carcass. The use of these tire bead rings inhibits the bead-bearing ends of the assembled tire carcass from rolling over to, in effect, seek the diameter of the tire carcass and also inhibits delaminations from occurring between the tire bands and the multiple beads. However, the presence of these bead rings have prevented the drum from being collapsed to a diameter sufficiently small to permit the removal of the tire carcass from the drum. To overcome this difficulty, tire bead rings were previously formed of a plurality of discrete arcuate ring segments which were removably supported on the drum so that upon completion of the tire carcass assembly, the bead ring segments could be individually detached from the drum and removed by hand so that the drum could be collapsed to a diameter sufficiently small to permit removal of the assembled tire carcass from the drum. These previous practices were found to be time consuming, extremely hazardous, and relatively expensive so as to considerably detract from the manufacture of high profile tires.